[hider=Long Rant About Arcosians and Genetics and Such Forth]
I'm well aware of how many humans are needed for genetic viability in the long term, [@Terminal]. I'm also aware that a lot of assumptions have been made about Frieza's race both in this RP and by the fandom in general - for instance, that he and his family are in fact Arcosians, which, whilst something I wouldn't disagree with, has never been explicitly confirmed by Toriyama; and the fact that all of them are absurdly powerful by everyone else's standards, as it's evidently the case in canon that only Cold and his line are ultra-powerful mutants (though this would obviously be the case even if the average Arcosian PL was 25000), whilst the average Arcosian might be at around the same level as most other races, i.e. PLs anywhere from 5 to 5000, give or take however much you like. We've not been given much to work with, after all - three individuals, and one of them isn't even canon.

That said, I'm not too concerned about the issue of clans and how they fit together, since we've been given a set number of clans to work with (Red, Blue, Green and Yellow, plus the multi-ethnicity mixed bloods) in a manner that, from reading the fluff, suggests a relatively non-familial relationship between the first few members of each clan. The problem I have is that every single other race with a low population count has its reasons for being so low and possesses a way around that: humans obviously don't have problems with population count; androids also don't have population issues, and don't engage in sexual reproduction anyway beyond maybe the few who are actually 17 and 18-esque cyborgs, who even then would produce human or part-human children depending on sexual partner of choice; the Saiyan race was reduced to literally two breeding members relatively recently, and only survives because they can produce fertile hybrids with humans (which has tons of far-spanning implications all its own, by the by, but lets not get into that), though even that's ultimately going to lead to gene dilution to the point that the Saiyan portion of the gene count might as well be non-present; the Namekians went through a cataclysm not too long before canon events that reduced their population to a single productive member, who was lucky enough to be part of a race that could reproduce asexually, and subsequently became the father of nearly all Namekians alive as of the anime's events (and those of this game by extension), with a presumably quite small number of Namekians currently able or willing to produce new members of their own race on account of the Demon Clan's presence; all of the Majin were split from what basically amounts to a sentient superweapon, may or may not be capable of reproduction, have no apparent interest in doing so at this stage, and may in fact be immortal anyway; and the Makaioshin were presumably born out of fruit in the same way as the standard Shin-jin, and are almost completely unique entities even when compared to one another.

The Arcosians have neither a reason nor a workaround explained for their population size - it is true that they've fought between clans on a planet with few resources in their early days, but there's been plenty of time for population numbers to rise given Frieza's apparent age, and by extension the ages of both King Cold and this game's Lord Shiver as well as the period of time they've been active for, and the abundant availability of resources on planets within the PTO, most of which seem to be fertile enough to produce life. Just to clarify the above statement, Frieza's age during DBZ has been estimated to be at least 70; thus, given that Shiver is "merely" about 115 years older than him, and assuming both he and Cold took an average amount of time to achieve their status as legally breeding adults, he probably took over as the Arcosian Lord fairly early on in his life, especially if the child he had with a Red Clan woman was in fact Cold's father and not Cold himself. My point is, there's not much reason for them to be so low in population, and since it's been very clearly established that they breed sexually, similar genes will recursively concentrate into future generations over time via inbreeding (and probably already have, if 100 members is where they are now, made worse by what is literally ethnic segregation), highly increasing the risk of birth defects simply due to the increased likelihood that both parents possess recessive genetic mutations that would result in such a defect... or, as the case may be, mutations that grant absurd power, though even that's not necessarily as true given that said mutation came from a pairing between two different ethnicities of the same race.

Incidentally, we don't know if a PL of 18000 would have been capable of actually destroying Earth, never mind flash-atomising it as you stated. That said, I don't necessarily disagree with you on that front, when PLs as low as 100-300 are capable of destroying orbiting celestial bodies from the planet's surface, even if they are small ones.
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